Researchers Cram More Info into Fiber Optics

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Fiber-optic cables that deliver Internet service are almost
filled to the brim with data, but a novel experiment has
demonstrated that they may be able to carry much more. By
changing a property called spin of the light waves that transmit
information, researchers have discovered a way to not only store
more information, but send it over long distances reliably.

The research comes by way of a new paper, published in this
week's issue of Science. "The
Internet has been growing at an exponential rate," Siddharth
Ramachandran, associate professor of electrical and computer
engineering at Boston University and co-author of the paper, told
TechNewsDaily.

"Fiber-optic transmission lines and fiber-optic communications
have been the backbone that serves this bandwidth, but
unfortunately, it has not been growing as fast as the demand has
been growing," he added.

Internet providers deliver service through fiber-optic cables:
extremely thin glass or plastic tubes that transmit light. Since
light is the fastest phenomenon in the universe and contains many
different wavelengths,
fiber optics can deliver tons of data at almost instantaneous
speeds.

"In fiber optics, we can send light at different colors and keep
them separate at the end of the line," Ramachandran said. In the
past, when engineers wanted to send more information than can be
handled by the current crop of colors, "we would just add another
color [and] call it multiplexing."

Multiplexing is a process in which a "fast" connection — like a
fiber-optic cable — transmits a jumble of data to a decoding
device. This device then transmits clear information to computers
via "slow" connections, like Ethernet cables.

There is a limit to the number of colors that can be sent down a
fiber, however, which meant that providers have already
almost saturated the fiber-optic cables with information. To
address this issue, Ramachandran and his team applied a principle
called "orbital angular momentum" (OAM) to spin fiber-optic
photons in a different fashion and fit more data in
transmissions.

Applying OAM to photons creates a number of new "spatial modes,"
which essentially act as channels to contain data.
"[Photons] move corkscrew down the fiber," Ramachandran said. "If
we design the fiber properly, we can make these modes very
stable."

The experiment demonstrated much more than stability. OAM-treated
fibers successfully transmitted data across 1.1 km of cable with
a speed of 400 gigabits per second across 4 discrete channels.
While the research is a long way from reaching consumers,
Ramachandran foresees numerous everyday applications. [See also:
Top 10 Life-Changing Inventions ]

"Smartphones and HDTVs require a huge [amount of]
bandwidth," he said. "In order for more apps to develop in
that space, one would need bandwidth to be scaling at an
exponential rate." If engineers can apply OAM to discover
additional fiber-optic channels, bandwidth and speeds can
continue to increase, and more people can use broadband.

Although this research deals with terrestrial Internet
connections, mobile networks are facing a similar problem: The
air is running out of viable data transmission frequencies.
Ramachandran foresees applications for OAM in this space as well.

"In free space, there are multiple ways by which one could use
OAM," he said. "At the receiving end, I can very easily detect
and figure out what the OAM state is, and from a data
communications standpoint … I can send it into a receiver and
decode the 1s and 0s."

As more of the world adopts broadband Internet, making room for
new data channels will be more important than ever. If this
experiment is any indication, OAM may play a pivotal role in
keeping fiber optics fast and efficient.